Cloning of Maize Transposon into Reveals the Polychromatic Sequence Landscape of Refractorily Propagated Plasmids.

, the founder member of the superfamily and its MURA transcripts, has been identified as toxic sequences to (), which heavily hindered the elucidation of the biochemical features of MURA transposase and confined the broader application of the system in other organisms. To harness less constrained systems as alternatives, we attempted to clone and two recently isolated autonomous -like elements () from maize, respectively. Their full-length transcripts and genomic copies are successfully cloned when the incubation time for bacteria to recover from heat shock is extended appropriately prior to plating. However, during their proliferation in , transformed plasmids are unstable, as evidenced by derivatives from which frameshift, deletion mutations, or IS transposon insertions are readily detected. Our results suggest that neither leaky expression of the transposase nor the presence of terminal inverse repeats (TIRs) are responsible for the cloning barriers, which were once ascribed to the presence of the Shine-Dalgarno-like sequence. Instead, the internal sequence of (from 1250 to 2845 bp), especially the exons in this region, was the most likely causer. The findings provide novel insights into the property and function of the superfamily and shed light on the dissection of toxic effects on cloning from .